When an electric vehicle is not being driven, the BMS needs to be in power-off state or low-power state. Otherwise, the automotive lead-acid battery, which power to the BMS, will be discharged to the over-discharge state to damage the lead-acid battery itself and cause the electric vehicle fail to start at the next time. When the BMS is power-off, it needs to be powered manually when it is power-off and the lithium battery pack needs to be charged, which is very inconvenient. Thus, the best choice is that the BMS maintains the low-power state, and when the lithium battery pack needs to be charged, the charger will wake up the BMS to work. Moreover, the BMS is powered by the charger to protect the lead-acid battery from over-discharging. In this situation, the wake-up circuit is required.